Compact Imaging Lens with Diffractive Surface for Mobile Devices
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Solution Overview
Problem
Existing imaging lenses for mobile devices face challenges in achieving compactness, thinness, and wide angle of view while maintaining high resolution and correcting aberrations, particularly due to the difficulty in shortening total track length and increasing manufacturing error sensitivity with current lens configurations.
Innovation Solution
The imaging lens configuration consists of five lenses with all surfaces being aspheric, where four lenses have positive refractive power and one lens has negative refractive power, along with a diffractive optical surface to correct chromatic aberrations, optimizing the distribution of refractive power to minimize lens thickness and manufacturing errors, and using plastic materials to reduce cost and improve productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple negative refractive power lenses are used to correct chromatic aberration, then chromatic aberration correction is improved, but total track length increases and device thinness deteriorates
Solution Approach 1:
The patent changes the material parameter by using plastic lenses with specific refractive indices (1.50 < Nd < 1.65) and Abbe numbers (20 < νd < 70) instead of traditional glass materials. This parameter change allows achieving chromatic aberration correction with positive refractive power lenses, eliminating the need for multiple negative lenses and thereby shortening the total track length while maintaining device thinness.
2Length of stationary object
If positive lens refractive power is increased to shorten total track length, then total track length is reduced, but manufacturing error sensitivity increases and productivity decreases
Solution Approach 1:
The patent optimizes the refractive power distribution among five lenses with positive refractive power, ensuring each lens has moderate refractive power rather than concentrating it in one lens. This balanced distribution, combined with using plastic materials with controlled refractive indices (1.50 < Nd < 1.65), reduces manufacturing error sensitivity while achieving a compact total track length of 4.0 mm or less.
Solution Approach 2:
The patent divides the total refractive power into five separate lenses, each contributing a portion of the overall positive refractive power. This segmentation prevents any single lens from having excessive refractive power, thereby reducing manufacturing error sensitivity and improving productivity while maintaining a compact form factor.
3Power
If curvature radius of lens surface is decreased to increase positive refractive power, then refractive power is improved, but manufacturing error sensitivity increases
Solution Approach 1:
The patent uses plastic materials with specific refractive index ranges (1.50 < Nd < 1.65) to achieve the required refractive power with larger curvature radii compared to glass materials. This material parameter change allows obtaining adequate refractive power without excessively small curvature radii, thereby reducing manufacturing error sensitivity and improving production feasibility.
4Manufacturing precision
If glass material is used for lenses, then optical performance is improved, but cost increases and mass production becomes difficult
Solution Approach 1:
The patent specifies plastic materials with controlled refractive indices (1.50 < Nd < 1.65) and Abbe numbers (20 < νd < 70) as alternatives to glass materials. These plastic materials can be molded using injection molding technology, enabling mass production at lower cost while maintaining adequate optical performance for mobile device applications.
Solution Approach 2:
The patent adopts plastic lens materials that are cheaper and easier to manufacture in large quantities compared to glass materials. Although plastic may have slightly different optical properties, the specified parameter ranges ensure adequate performance for consumer electronics applications where cost-effective mass production is critical.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration results in a compact and thin imaging lens with a total track length of 4.0 mm or less, achieving a wide angle of view and high brightness while effectively correcting various aberrations, and allowing for mass production at a lower cost.
Implementation Method 1
a diffractive optical surface is formed on one of three surfaces from the image-side surface of the first lens to the image-side surface of the second lens
Implementation Method 2
all the lens surfaces are aspheric
Data Source
AI summary
An imaging lens which can be very compact and thin, corrects various aberrations properly and provides a small F-value and a wide view angle at low cost. In the imaging lens, designed for a solid-state image sensor, arranged in the following order from an object side to an image side are: a first positive (refractive power) lens with a convex object-side surface; a second positive lens; a third positive lens; a fourth positive lens; and a fifth negative lens with a concave image-side surface. None of these lenses is joined to each other and all the lens surfaces are aspheric. The object-side and image-side aspheric surfaces of the fifth lens have a pole-change point in a position other than a point of intersection with an optical axis. A diffractive optical surface is formed on one of three surfaces from the first lens image-side surface to the second lens image-side surface.